Rear Wing Aero Design Theory

[jaycar]

Have read F1 Technical before, but this is my first post, pretty excited!
Now down to business, I am looking at rear wing design theory and was looking for some help or some good resources to take a look at. My primary interest is in slots and slats.
Slots: Gaps in the endplates above the airfoils to bleed high pressure, reducing the pressure delta and reducing drag. WHY they are used I have a grasp on, but what I find interesting are all the different slot designs. Fewer slots seem to be used on high speed tracks, and each team has their own approach. The root of my problem is: why would a team go with a particular design, as in why are some slots almost all horizontal ( https://thewptformula.files.wordpress.c ... dplate.jpg ) versus other that are closer to vertical ( https://thewptformula.files.wordpress.c ... dplate.jpg ). Any insight into slot sizing, spacing, and orientation would be greatly appreciated.
Looking back at the latter picture, why is it increasingly common for teams to have endplate geometries that cut down after the 2nd element, only to slope back up again (the red bull wing in the 2nd link above).What is the reasoning behind this?

Any help is appreciated, thanks a lot!

[godlameroso]

Simply put, you only put as many slots in the wing as you need to bleed the amount of pressure you want, and you angle them to bleed them in the direction you want. The way the slots are aimed will do different things with different part of the vortex formed at the endplates. They not only reduce drag but also improve the consistency of the downforce, remember the end plates work as an extension of the wing as such the large end plates have a tremendous effect on overall rear aero. Especially since there's no more beam wing, in fact you can see this year's cars and how intricate the RW end plates are in general.

[bhall II]

If I had to hazard a (barely) educated guess, I'd say that diagonal slots tend to constantly bleed pressure, and horizontal slots tend to bleed only excess pressure. So, by extension, diagonal slots are indicative of a design solution that favors efficiency, and horizontal slots are indicative of one that favors peak downforce. This hypothesis is based purely on the orientation of the slots relative to oncoming air flow.

Diagonal slots would appear to vent pressure any time the car is moving forward, regardless of conditions. In doing so, I imagine it helps reduce the strength of tip vortices.



Horizontal slots, on the other hand, seem to require something more than forward motion -- like increased pressure -- in order for air to flow through them. In other words, they bleed any pressure above and beyond a certain level.

(Given the recent restrictions to curtail downforce, especially at the back of the car, e.g. no beam wing, smaller rear wing, it might be telling that only Manor/Marussia uses diagonal slots, and they do so on a car that's more than a year old.)



And I guess you could consider the wing below to be a hybrid of sorts.



Red Bull experimented with a slot-less design last year that incorporated unorthodox slots placed under the wing in order to equalize pressure on both sides of the end plate to reduce the strength of tip vortices. Ferrari and McLaren adopted that feature this year.



DRS is obviously a factor. But, my bio-CFD lacks the processing power needed to discern the relevant interactions.

Looking back at the latter picture, why is it increasingly common for teams to have endplate geometries that cut down after the 2nd element, only to slope back up again (the red bull wing in the 2nd link above).What is the reasoning behind this?

If you're referring to the feature below, I think it maximizes effective wingspan by taking advantage of regulations that allow for reasonably thick end plates.

[ESPImperium]

Bleed pressuure and stop a aerodynamic dam being formed in front of the wing element and gain downforce and improve the efficiency of the downforce of the rear wing. However the aerodynamic dam on slotless end plates is advantageous at low/lower downforce tracks like Canada and Monza where aero isn't really needed as there is no 'high speed' section. The Red Bull Ring and Spa are high speed tracks that are lower downforce tracks that need the efficiency for instance, Montreal and Monza are low downforce low efficiency tracks as you need more raw top speed, Spa and Red Bull Ring need a low downforce high efficiency rear wing.

However, there are tracks that require high downforce high efficiency rear wings for the likes of Hungary, how tracks that are like Monaco that require high downforce but low efficiency wings in order to achieve the highest peak downforce achievable, as opposed to Hungary that requires the highest achievable but useable downforce.

In honesty, now there is not really much of a difference now in rear end downforce from the rear wing from low to high for each team, probably about 300-350kg from each variation in a team. However, this will differ as much as that from Manor to Mercedes. In effect Mercedes lowest downforce wing will be producing as much, if not a little more as Manors highest downforce wing, even if Manor have only one wing to use at Monaco and Monza, where Mercedes will have as many as 8 or 9 wing variations. This can be worth as much as a second a lap, depending on the track.

There isn't much between the cars, however in terms of weight from downforce, there will probably be around 1,000 kilos between the top end and the tail end, this will be easily 5 seconds a lap. Every 200kilos will be worth a second a lap, depending on if the team is using efficient or in-efficient wings, most of them now are efficient with inefficient wings being used sporadically through the season.

[trinidefender]

Bleed pressuure and stop a aerodynamic dam being formed in front of the wing element and gain downforce and improve the efficiency of the downforce of the rear wing. However the aerodynamic dam on slotless end plates is advantageous at low/lower downforce tracks like Canada and Monza where aero isn't really needed as there is no 'high speed' section. The Red Bull Ring and Spa are high speed tracks that are lower downforce tracks that need the efficiency for instance, Montreal and Monza are low downforce low efficiency tracks as you need more raw top speed, Spa and Red Bull Ring need a low downforce high efficiency rear wing.

However, there are tracks that require high downforce high efficiency rear wings for the likes of Hungary, how tracks that are like Monaco that require high downforce but low efficiency wings in order to achieve the highest peak downforce achievable, as opposed to Hungary that requires the highest achievable but useable downforce.

In honesty, now there is not really much of a difference now in rear end downforce from the rear wing from low to high for each team, probably about 300-350kg from each variation in a team. However, this will differ as much as that from Manor to Mercedes. In effect Mercedes lowest downforce wing will be producing as much, if not a little more as Manors highest downforce wing, even if Manor have only one wing to use at Monaco and Monza, where Mercedes will have as many as 8 or 9 wing variations. This can be worth as much as a second a lap, depending on the track.

There isn't much between the cars, however in terms of weight from downforce, there will probably be around 1,000 kilos between the top end and the tail end, this will be easily 5 seconds a lap. Every 200kilos will be worth a second a lap, depending on if the team is using efficient or in-efficient wings, most of them now are efficient with inefficient wings being used sporadically through the season.

Sorry but what? An aerodynamic dam? Never in my life have I heard of such a thing. The slots bleed high pressure above the wing to the nominal pressure area next the rear wing end plates (RWEP). Reducing this pressure reduces downforce but it also reduces drag considerably by the reduction in strength of the vortices at the top of the RWEP.

As to why they are shaped the way they are is something interesting that I have been looking at for a while. The problem is, unlike many other things on F1 related to aerodynamics in aircraft, there is very little information available about them. Much of aerodynamics in F1 has been pioneered in aviation but this seems to be a concept almost exclusive to F1.

Here is something, as well as just the shape and design of the end plate slots, look at the design of the end plates behind the rear wing. Some are high, some low, some slope down and some slope up. The trend is for them to be flat now. This shape influences how the low pressure between the end plates interact with the nominal (but higher) pressure airflow outside the endplates. It also has an influence on the strength of the vortex coming off of the RWEP to the degree of sometimes creating a counter rotating vortex.

[bhall II]

Here is something, as well as just the shape and design of the end plate slots, look at the design of the end plates behind the rear wing. Some are high, some low, some slope down and some slope up. The trend is for them to be flat now. This shape influences how the low pressure between the end plates interact with the nominal (but higher) pressure airflow outside the endplates. It also has an influence on the strength of the vortex coming off of the RWEP to the degree of sometimes creating a counter rotating vortex.

To sorta go along with that, I think the major effect is the measure of control they allow with regard to flow separation. You could create more downforce without those cutouts, and the additional drag penalty wouldn't necessarily be prohibitive. However, the extreme AoA would make it very sensitive.

The solution then is to reduce the dynamic pressure of air flow under the wing in order to trip the boundary layer at a point just before it becomes unstable. The result is less downforce, but it's much more consistent.



If you ever get really, really bored, look through a bunch of photos of rear wing end plates. You'll see that a high percentage of cutouts are seemingly oriented toward a position that's 1/4-chord length behind the leading edge of the second element. (Or you can just move to a town with a population higher than 440 and do something that's actually productive.)

(Help me.)